Arnold T. Nielsen in a paper entitled "Synthesis of 2,4,6,8,10,12-Hexabenzyl-2,4,5,6,10,12-hexaazaisowurtzitane" describes the synthesis of the compound named in the title. This compound is hereinafter referred to as HBIW. The more formal chemical name for this compound is 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazatetracyclo-[5.5.0.0..sup.3,1 1 0..sup.5,9 ]dodecane. Nielsen et al. in documents entitles "Polynitropolyaza Caged Explosives Parts 5 & 6" (Part 6 is classified) and "synthesis of a caged nitramine" (classified) prepared for the Naval Weapons Center, China Lake, Calif., describe the synthesis of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaayatetracyclo[5.5.0.0..sup.3,11 0..sup.5,9 ]dodecane which is known in the propellent/explosives field as CL-20 (This compound is hereinafter referred to as CL-20). The above-identified works of Nielsen and Nielsen et al. are incorporated herein by reference.
CL-20 is an oxidizer with great potential for use in high-energy compositions, such as propellants, gassifiers, explosives or the like. CL-20 has high detonation velocity attributable to its high heat of formation. It is also advantageous because of its high density, which is a result of the cage structure. It has particular usefulness for minimum smoke formulations (generally non-aluminized formulations). It also has particular usefulness in explosive compositions.
HBIW has the following chemical structure; the indicated numbering of the carbon and nitrogen ring members are understood to apply throughout the specification. ##STR1##
It is to be noted in the above formula that the identical 2, 6, 8, and 12 cage nitrogens are members of 5 and 6 member rings, whereas the 4 and 10 cage nitrogens are members of 6 and 7 member rings. It is found that in many chemical reactions, the four identical nitrogens react differently than the two identical nitrogens. These different nitrogens will be referred to hereinafter as the 2-6-8-12 nitrogens or the 4-10 nitrogens, respectively.
CL-20 has the following chemical structure: ##STR2##
In the first step of the procedure of converting HBIW (I) to CL-20 (II), HBIW is converted to 2,6,8,12-tetraacetyl-4,10-dibenzylhexaazaisowurtzitane, hereinafter referred to as compound IIIA, (also referred to herein as TADB) having the formula shown below: ##STR3##
The transformation from HBIW (I) to Compound IIIA is effected for example, with hydrogen in the presence of a palladium hydroxide-on-carbon catalyst and acetic anhydride using a bromobenzene catalyst. Subsequent conversion of Compound (IIIA) to CL-20 is effected using, in succession, the nitrating agents NOBF.sub.1 and NO.sub.2 BF.sub.1. These nitrating agents are very expensive. Also because of the fluorine present, waste products pose significant environmental problems. The expense of producing CL-20 by this synthesis is a significant limitation to its general usefulness in the propellant and explosive industries.
Accordingly, it is a general object of the invention of provide methods of syntheses of CL-20 and related energetic compounds, which methods are an improvement from the standpoint of cost and environmental impact.
It is a further object of the invention to provide novel chemical intermediates which can be converted to CL-20 and related high-energy caged nitrogen compounds.